1. Power
Reduce power on all engines to idle. In a multi-engine aircraft, you can also add power to the inboard engine to help stop the rotation.
2. Ailerons
Center the ailerons / ailerons to neutral, or remove any aileron input. This helps to even out the angle of attack on the wings, reducing rolling and yawing motions.
3. Rudder
Apply full rudder deflection in the opposite direction of the spin. For example, if the aircraft is spinning left, apply right rudder. Once the spin stops, you can neutralize the rudder. [Edit] - May sound obvious and redundant as the above states “… for example…”, but here is Peter Rounce’s remark: recognize first direction you are spinning and then apply correct opposite rudder (same concept, but now on his words)
4. Elevator
Apply forward elevator, or up to full control deflection if needed, to reduce the angle of attack and unstall the wing. Once the rotation has stopped, you can apply back pressure on the elevator to gently recover from the dive.
[Edit] - Remark by Peter Rounce - how fast you apply the elevator will make a difference - you can crossover from upright to an inverted spin if you do it too quickly.
After completing these steps, you can adjust the power and elevator inputs to return the aircraft to level, controlled flight. Note - it is OBVIOUS that these are summarized instructions which are by no means deemed to be complete and a replacement to actual unusual attitudes training. It is impossible to handshake it all on a post.